An air-side economizer is an accessory to an HVAC system that enables it to run more economically. Economizers proportionally blend return air drawn from the indoor space of a building and outdoor air drawn from outside the building to make the overall enthalpy of the blended air as low as reasonably possible and to comply with building ventilation codes that exist in virtually every jurisdiction. Economizers have two damper assemblies: a return air damper for the return air and an outdoor air damper for the outdoor air. When the return air damper is fully closed, the outdoor air damper is fully open. As the return air damper is opened, the outdoor air damper is closed. When the return air damper is fully open, the outdoor air damper is fully closed. As the outdoor air damper is opened, the return air damper is closed.
Each damper is an assembly having a plurality of elongated damper blades that rotate about their major axis as the damper is opened and closed. Conventional economizers come in two varieties: those in which all of the damper blades of both damper assemblies move in parallel and those in which adjacent damper blades of both damper assemblies move in opposition. Conventional economizers work reasonably well and are becoming evermore popular as energy costs rise and customers look for ways to decrease costs and help the environment.